JPS5934442B2 - Hot rolling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to reduce edge drop and improve the product quality of hot-rolled materials without large-scale modification of equipment.

In general, the shape of a rolled plate has flatness issues such as ear waves and mid-elongation, and variations in thickness in the width direction (profile), and the profile also has problems with crowns and edge drops.

By the way, the profile is largely determined by the shape of the roll gap, but the deflection, initial crown, thermal crown, and wear of the work roll affect the plate crown, and the work roll dents near the edge of the plate and protects the plate. It is thought that this has a large effect on the edge drop of the board.

There are two ways to control the above profile: operational and mechanical.
There are adjustments to the rolling pitch and reduction distribution for each stand, and the rolling mill mechanisms include an initial roll crown, work roll venter, backup roll bender, and coolant control.

However, none of the above methods is effective against edge drops.

On the other hand, in order to solve the above problems, there have been proposals for rolling mills equipped with various shape control mechanisms, but these are not necessarily effective.

By the way, FIG. 1 shows the state of rolling by a conventional 4Hi mill, and as shown in this figure, the edge drop portion E
It can be seen that the shape is due to the depression of the work roll 2a at the end of the plate of the material 4 to be rolled.

The present invention has been completed after research focusing on the shape of the work roll at the edge of the plate.

That is, the present invention provides at least a pair of vertical rolls in front of at least one rolling stand of the finishing rolling mill group when performing hot finish rolling, and adjusts the amount of rolling of the vertical rolls to the rolling amount at the entrance side of the vertical rolls. This hot rolling method is characterized in that edge drop can be reduced by rolling the material to within 1/2 of the thickness of the material.

According to the present invention, vertical rolls can be applied to either the front stage, the rear stage, or the entire hot finishing mill group.

In addition, the rolling reduction amount of the vertical roll, that is, the plate width at the entrance of the vertical roll is Wl (mm ), and the plate width at the outlet of the vertical roll is W2 (
mrn ), then (Wt - W2 ) (mr
rt) is preferably within 1/2 of the thickness of the material to be rolled at the entrance of the vertical rolls, and buckling occurs if it exceeds 1/2 of the thickness of the material to be rolled at the entrance of the vertical rolls. It should be avoided as it will reduce the product value.

FIG. 2 is a side view of a finishing rolling mill used in carrying out the method of the present invention, and FIG. 3 is a plan view thereof, showing a pair of vertical rolling rolls 3a for rolling the material to be rolled 4 in the width direction; 3b, and immediately after that, upper and lower work rolls (WR) 2a and 2b that horizontally roll the material to be rolled 4, and backup rolls (B, U,') that reinforce the work rolls 2a and 2b, respectively. R) Ia and 1b are arranged.

The vertical rolling rolls 3a, 3b are adjusted in advance so that the rolling reduction amount thereof is within 1/2 of the thickness of the plate 4 to be rolled.

In this way, the rolled material 4 whose cross-sectional profile before finish rolling is shown by the solid line (A) in FIG.
When passing between a and 3b, the vertical rolling roll 3a,
3b in the width direction, the end portion of the plate protrudes vertically as shown by the chain line (B) in FIG. 4, and a so-called dog bone is formed.

After that, when passing between the work rolls 2a and 2b, the dents and dog bones of the no-crawls 2a and 2b cancel each other out, resulting in the parallelism of the upper and lower surfaces as shown by the dashed line (C) in FIG. A rolled material with high

That is, as shown in FIG. 5, in the case of the method of the present invention, the recess of the work roll 2a due to the dog bone is larger than the recess of the work roll during conventional rolling, as shown by the solid line A, so that the edge drop E1 according to the present invention is formed. is smaller than the conventional edge drop E2.

As described above, the present invention includes a pair of vertical rolls sandwiching a material to be rolled on the entry side of a finishing rolling mill, and the rolling amount of the vertical rolls is set to 1 on the entry side of the vertical rolls. Since rolling is performed within 1/2 of the thickness of the material, the dogbone at the edge of the rolled material formed by the vertical rolls and the concavity between the work rolls are offset, resulting in a product with extremely low edge drop, which ranks #4. A finished rolled material can be obtained without requiring large-scale modification of equipment.

In the above description, a case has been described in which one pair of vertical rolls is provided, but edge drops can be reduced by providing several sets of vertical rolls in multiple stages.

Examples Finish rolling was carried out under the following conditions using the method of the present invention and the conventional rolling method using a 4Hi mill.

As a result, in the case of the method of the present invention, the edge drop is 2.
0 (μ), which was reduced to about 1/9 compared to the conventional method.

However, the target materials are as follows.

Steel type Low carbon steel Coil dimensions (mm) 2.00 X915 Finishing temperature G0 850 Coiling temperature CQ
640F2 is the front side of the second stage of the finishing mill.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing a conventional rolling state, Fig. 2 is a side view of a finishing rolling mill showing an embodiment of the present invention, Fig. 3 is a plan view thereof, and Fig. 4 is an illustration of a rolled material according to the present invention. FIG. 5 is an explanatory diagram showing the rolling state of the present invention and the conventional rolling state. In the figure, 3a and 3b are vertical rolls.

Claims (1)

[Claims] 1. When performing hot finishing rolling, at least one pair of vertical rolls is provided in front of at least one rolling stand of the finishing rolling mill group, and the rolling reduction amount of the vertical rolls is determined by the thickness of the material to be rolled at the entrance side of the vertical rolls. A hot rolling method characterized by making it possible to reduce edge drop by rolling within 1/2 of .